[grpc_clients] bump gRPC connection timeout to 30 seconds

Summary:
resolves https://linear.app/comm/issue/ENG-9300/bump-identity-service-timeouts

users with bad internet can sometimes see their client time out while talking to identity. it seems that 5 seconds was too short, so bumping to 30 seconds.

Test Plan: tested this in D10329. also tested the native app with increased timeout to confirm there are no regressions

Reviewers: ashoat, bartek, will

Reviewed By: will

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D13355